1. Field of the Invention
The present invention relates to a towable device that may be used to scrape and grade unpaved surfaces such as roadways and the like. More particularly, the present invention relates to a towable road tender (1) that is relatively lightweight; (2) that is readily useable behind small, private tractors and pickup trucks as well as with larger commercial vehicles; (3) that may be operated via convenient small-scale power take-off units, such as the hydraulic units of conventional front-end plow devices; and (4) that may be either centered directly behind the vehicle or set off to one side behind the vehicle. The preferred embodiment of the present towable road tender includes a lightweight frame, a set of pivotable rear wheels, an articulated attachment frame and a pivotable grading blade.
2. Description of the Prior Art
Road grading devices have been available for many years. Many types of road graders are used to complete the restructuring of rough terrain after preliminary smoothing initiated by heavy equipment such as bulldozers. This finish grading yields roadways that may or may not be paved. In most instances, commercially available road graders are of substantial size and weight and provide uniform, smooth leveling. Generally, these graders are single-unit devices that comprise a grading blade positioned under the vehicle operator, and the blade alone is powered upward or downward in order to contact the underlying surface.
Alternatively, there are grading devices that can be drawn behind powered vehicles instead of being made an integral component of such vehicles. These graders can therefore be shifted from one vehicle to another for greater operational flexibility. One example of such grading devices is the land leveler disclosed by Breaux in U.S. Pat. No. 2,866,281 (1958). Breaux describes a grading blade that is affixed to a combination frame which is in turn used to pivot the blade. Another example is the leveling apparatus described by Bailiff in U.S. Pat. No. 2,635,888 (1953). The Bailiff device is a wheeled assembly for a towed grader. The assembly provides for hydraulic operation of the lower portion of a jointed frame that raises and lowers the leveling blade by drawing in or extending the rear wheels. The upper portion of the frame is intended to be used as a trailer unit for transporting materials. The Hallam (U.S. Pat. No. 3,716,105--1973) towable grader highlights the usage of a particular coupling unit that permits the tractor towing the grader to turn in a relatively tight radius. All of the above-referenced disclosures fail, however, to provide a towed grader that may be oriented off-center, or offset, behind the towing vehicle. Such a design would permit the user to drive the towing vehicle safely on the roadway while leveling more precarious positions along the roadway edge without compromising the ability to turn in a tight radius when required.
The above-described towable grading devices, and others like them, provide a means for preparing roadway surfaces without resort to very expensive self-powered machinery. Nevertheless, even these towable devices exclude the typical private user from improving his or her own roadway, driveway and the like. In particular, the towable graders presently available are designed to be pulled behind a piece of heavy-duty equipment, such as an earth mover or commercial tractor, that is capable of moving and maneuvering an object weighing several thousand pounds, which object is often dragging an additional load of roadway dirt. The private user does not have ready access to such equipment and even with such access may not be capable of operating it. More commonly, the private user has a vehicle such as a pickup truck or small-scale tractor, acquired in order to complete common everyday projects. Such vehicles cannot be used to tow the prior art graders described--particularly when such graders are pulling additional loads during a leveling operation. Therefore, the prior art towable graders are not designed for the private user.
Another indication that most prior art graders are commercially oriented is the means by which they are operated. A number of them are operated hydraulically via lines extending from the towing vehicle. (See, for example, the dual-action hydraulic operation of the Bailiff wheel assembly.) The size of the prior towable graders at issue require a reservoir of several gallons of hydraulic fluid for proper operation. The heavy-duty towing equipment previously noted may be able to provide such capacity. At the very least, that equipment is designed to accommodate such additional capacity and to control the operation of hydraulically-powered graders from within the towing vehicle. On the other hand, the vehicles normally employed by the private user cannot readily accommodate such a supplemental reservoir of hydraulic fluid. Instead, such private vehicles would have to be modified considerably in order to provide for proper operation of the prior towable graders--assuming, of course, that such private vehicles had the physical capacity to haul them. That modification would drive up the overall cost of the grader and would probably compromise operation of the vehicle when the grader was not in use. Moreover, further modification would have to be carried out if the grader were to be operated remotely from the towing vehicle itself, an action that would further increase costs. Alternatively, a more suitable towed grader would be operable via systems readily available for private vehicles, such as, for example, the hydraulic units of front-end plowing devices.
There are available towable devices that may be used to "manicure" a roadway. These devices often comprise a screening rake that essentially scrapes loose material from the roadway and that may create small troughs in the roadway as well. These devices necessarily fail to fulfill the goal achieved with the prior art graders and levelers in that they are too lightweight to remove the top, rough layer of the roadway and then deposit the excess material where it may be lacking. The relatively small size of such screening devices allows for usage behind private towing vehicles of the type previously noted. This does not, however, overcome their inherent inability to restructure a roadway. In the scheme of things, such towable "screens" are at the opposite end of the spectrum from the heavy-duty towable graders noted.
There are devices available that might be considered suitable for use as tenders towable behind private vehicles. Typically, these devices are rake systems used for roadway screening. In some instances a grading blade may be affixed to the rake element and used in an attempt to level the roadway. These devices, even with attachable grader blades suffer from the fact that they weigh much less than the prior towable graders. Because of this weight reduction, the supplemental grading blade does not have the forcing load to "dig up" an old roadway in order to produce a level new surface. At best, only loosely-packed portions of the roadway can be drawn by the blade. In most instances, however, the blade simply bounces over hardened roadway sections. As a result, the roadway may become even less level than before use of the lightweight grading blade. Apart from this essential problem with small, towable rake systems, there are other problems which make them less than suitable for adequate road grading. In particular, these devices apparently have no means for 1) quickly and easily raising and lowering the blade when desired; 2) canting the blade to grade at an angle; and 3) offsetting the blade of the rake system to provide for leveling of precarious roadway edges.
One critical drawback that is evident in all of the earlier towable grading systems noted above is the means by which the towed device is connected to the towing vehicle. Specifically, many of the towable systems comprise elaborate connection devices which increase complexity as well as cost. For the private user, the goal is to minimize cost and reduce complexity. For that reason, it is most advantageous to use connection means that are already available on the towing vehicle. Generally, these means are either hitching balls or towing hooks. There are towable graders/screens that provide for ready connection to the towing vehicle in the manner noted. They all fail, however, to address the fact that when the grader is connected to the towing vehicle, the connection results in some cases a serious, and, in other cases, a slight, lifting of the grader unit from the roadway. This lifting is particularly pronounced when the towing vehicle is a pickup truck and the grader is considerably shorter than the rear of the truck. In this lifted position the blade's bearing on the roadway is reduced and so its leveling effectiveness is also reduced. The most common reason for this failure is the fact that the connecting bar between the hitch of the towing vehicle and the frame comprising the grading blade together form a unitary, straight piece. Because of this there is no means for counteracting the lifting effect of the connection. (See, for example, the attachment means of the Bailiff assembly and the more complex Hallam device.) If anything, this design requires, at the very least, a heavier grader frame in order to permit adequate road grading. A heavier frame may not be suitable for use behind the smaller private vehicles contemplated. Thus, both simple and complex towable grading devices have failed to eliminate this undesirable lifting in a relatively simple grader design.
Some attempts to minimize lifting effects have yielded fairly complex systems. In particular, the Breaux leveler includes an elaborate hydraulic system for raising and lowering the front end of the grader frame. This elaborate system does not, however, achieve the desired goal because there is no means for securing the articulated front arm to the towing hitch. Instead, a simple hook is used to complete the connection. As the articulated joint of the frame is pivoted, the attachment hook simply rotates on the towing hook. This may or may not eliminate the upward lifting effect entirely. In any event, the complex Breaux attachment fixture does not take advantage of the towing vehicle's weight as a way of translating supplemental vertical loading force to the grading blade.
A more effective road-tending device would be one of relatively light weight so that the towing load on the towing vehicle would be minimized. At the same time, the device would take advantage of the towing vehicle's own weight in order to provide a bearing load to the grading blade. Prior single-unit graders had such an advantage, primarily because the grading blade was an integral part of the moving vehicle. On the other hand, towable tenders do not have this luxury and are necessarily a compromise between towing weight and leveling capability. The prior art towable graders have failed to effectively achieve this compromise, however, particularly with regard to graders usable behind common private vehicles. Therefore, what is needed is a towable road grader (tender) that may be readily deployed behind small private vehicles such as pickup trucks. What is also needed is a towable road tender that is lightweight and that takes advantage of the towing vehicle's weight to provide bearing load to the tending tool. Further, what is needed is a towable tender that may be pulled either centered directly behind the towing vehicle or offset from center. Still further, what is needed is a towable tender that may be operated using power systems readily available for private vehicles, such as, for example, those hydraulic units provided with conventional front-end plow devices.